Sheet folding apparatus

ABSTRACT

A buckle ( 3, 4 ) is provided with a position adjustable stopper ( 5, 6 ) for stopping a sheet (P) by coming into collision with the leading edge of the sheet (P) so as to position the sheet in a fold position. In the inlet of the buckle, there are provided a pair of rotary drive folding rollers ( 20   a,    20   b;    20   c,    20   d ) for taking the sheet in the buckle, and a pair of rotary drive folding rollers ( 20   b,    20   c;    20   d,    20   e ) for folding a portion of the sheet deflecting from the buckle. A sheet detector ( 16, 17 ) is arranged in the buckle at a predetermined spacing from the stopper. A control section ( 29 ) outputting a signal for deceleration to a driving source of the roller upon reception of a sheet detection signal from the sheet detector and stopping output of the signal for deceleration after elapse of a predetermined time. After the leading edge of the sheet introduced into the buckle passes through the sheet detector, the rotational speed of the roller is reduced to decrease the conveying speed of the sheet, the leading edge of the sheet collides with the stopper at a sufficiently reduced speed, thereafter, the rotational speed of the roller is gradually increased so that the rotational speed before being reduced is recovered when the next sheet is introduced into the buckle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet folding apparatus.

2. Description of the Related Art

A conventional sheet folding apparatus has at least one buckle in whicha sheet to be folded is introduced to a length corresponding to apredetermined fold position. The buckle is provided with a positionadjustable stopper for stopping the introduced sheet by coming intocollision with the leading edge of the sheet so as to position the sheetin the fold position. Near the inlet of the buckle, a pair of rotatingrollers are arranged oppositely to each other for taking the sheet inthe buckle and a pair of rotating rollers are arranged oppositely toeach other for folding a portion of the sheet deflecting from thebuckle.

The sheet folding apparatus typically folds 100 or more sheets perminute. Each of the sheets collides with the stopper of the buckle at aspeed of 900 mm per second, and at the same time, is deflected in thebuckle to contact with the inner wall surface of the buckle. The noiseof the collision and the noise of the contact of the sheet with theinner wall surface of the buckle together with the noise of sheetnipping of the rollers cause a noise problem in the installationlocation for the sheet folding apparatus such as an office.

In order to reduce such noise, there is proposed a method of attachingan elastic member for relieving any impact at a time of collision to thefront surface of the stopper of the buckle (see Japanese Laid-OpenPatent Publication No. H11-106127). There is also proposed a method ofreducing the speed of a sheet in such a manner that an elastic slide isarranged ahead of the stopper of the buckle for coming into collisionwith the leading edge of the sheet (see Japanese Laid-Open PatentPublication No. 2004-345773).

These methods can reduce the noise of collision of the sheet with thestopper, but cannot reduce the noise of the contact of the sheet withthe inner wall surface of the buckle and the noise of sheet nipping ofthe rollers. Consequently, the noise level at operation cannot beimproved much. In addition, the movement of the stopper provided withthe elastic member and the elastic slide is not smooth, which brings theresult that the stop position of the sheet in the buckle fluctuates, sothat the fold position of the sheet can be easily misaligned.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a sheet foldingapparatus capable of achieving considerably low level of the noise atoperation thereof and ensuring a stable fold position of a sheet.

In order to achieve the object, in accordance with the presentinvention, there is provided a sheet folding apparatus having: at leastone buckle in which a sheet to be folded is introduced to a lengthcorresponding to a predetermined fold position, the at least one bucklebeing provided with a position adjustable stopper for stopping theintroduced sheet by coming into collision with the leading edge of thesheet so as to position the sheet in the fold position; a pair ofrotating rollers arranged near the inlet of the buckle and oppositely toeach other for taking the sheet in the buckle; and a pair of rotatingrollers arranged near the inlet of the buckle and oppositely to eachother for folding a portion of the sheet deflecting from the buckle, thesheet folding apparatus characterized by a sheet detector arranged at apredetermined spacing from the stopper of the buckle toward the inlet ofthe buckle and detecting passage of the sheet; and a control sectionoutputting a signal for deceleration to a driving source of the rollerupon reception of a sheet detection signal from the sheet detector andstopping output of the signal for deceleration after elapse of apredetermined time, whereby, after the leading edge of the sheetintroduced into the buckle passes through the sheet detector, therotational speed of the rollers is reduced to decrease the conveyingspeed of the sheet, the leading edge of the sheet comes into collisionwith the stopper at a sufficiently reduced speed, and thereafter therotational speed of the roller is gradually increased so that therotational speed before being reduced is recovered when the next sheetis introduced into the buckle.

Alternatively, in order to achieve the object, in accordance with thepresent invention, there is provided a sheet folding apparatus having:at least one buckle in which a sheet to be folded is introduced to alength corresponding to a predetermined fold position, the at least onebuckle being provided with a position adjustable stopper for stoppingthe introduced sheet by coming into collision with the leading edge ofthe sheet so as to position the sheet in the fold position; a pair ofrotating rollers arranged near the inlet of the buckle and oppositelyeach other for taking the sheet in the buckle; and a pair of rotarydrive rollers arranged near the inlet of the buckle and oppositely toeach other for folding a portion of the sheet deflecting from thebuckle, the sheet folding apparatus characterized by a sheet detectorarranged upstream of the pair of rollers for taking the sheet in theuppermost stream buckle for detecting passage of the sheet; a rotaryencoder mounted on at least one rotating shaft of the rollers arrangednear the inlet of the buckle or at least one another rotating shaftrotatable in conjunction with the rotating shaft of the rollers; and acontrol section starting counting the number of pulses outputted fromthe rotary encoder upon reception of a sheet detection signal from thesheet detector to measure the conveying distance of the sheet,outputting a signal for deceleration to a driving source of the rollerwhen the sheet reaches a predetermined position, and stopping output ofthe signal for deceleration when the sheet reaches the nextpredetermined position, whereby, after the leading edge of the sheetpasses through the sheet detector, the rotational speed of the roller isreduced to decrease the conveying speed of the sheet, the leading edgeof the sheet comes into collision with the stopper at a sufficientlyreduced speed, and, thereafter, the rotational speed of the roller isgradually increased so that the rotational speed before being reduced isrecovered when the next sheet is introduced into the buckle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view illustrating the configuration of a sheet foldingapparatus according to a first embodiment of the present invention;

FIG. 2 is an enlarged side view illustrating the configuration around abuckle of the sheet folding apparatus of FIG. 1;

FIG. 3(A) is a timing diagram of control of rotational speed of a motorby a control section;

FIG. 3(B) is a diagram illustrating sheet positions at points (i) and(ii) of the timing diagram of FIG. 3(A);

FIG. 4 is a side view illustrating the configuration of the sheetfolding apparatus according to another embodiment of the presentinvention;

FIG. 5(A) is a timing diagram of control of rotational speed of a motorby a control section; and

FIG. 5(B) is a diagram illustrating sheet positions at points (i) and(ii) of the timing diagram of FIG. 5(A).

DETAILED EXPLANATION OF PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described belowwith reference to the accompanying drawings. FIG. 1 is a side viewillustrating the configuration of a sheet folding apparatus according toa first embodiment of the present invention, and FIG. 2 is an enlargedside view illustrating the configuration around a buckle of the sheetfolding apparatus of FIG. 1.

Referring to FIGS. 1 and 2, the sheet folding apparatus of the presentinvention has a sheet supply table 1 arranged for up-and-down movementand supporting a sheet bundle of sheets P to be folded thereon, avertical plate 1 a disposed ahead of the sheet supply table 1 andaligning the leading edge of the sheet bundle on the sheet supply table1, and a sheet feed roller 2 sequentially feeding the uppermost sheet Pof the sheet bundle on the sheet supply table 1.

The sheet folding apparatus also has first and second buckles 3 and 4 inwhich the sheet P is introduced to a length corresponding to apredetermined fold position. As illustrated, the first and secondbuckles 3 and 4 have a pair of plates 3 a, 3 b; 4 a, 4 b arrangedoppositely to each other at a small spacing therebetween.

The first and second buckles 3 and 4 have stoppers 5 and 6 bringing theleading edge of the sheet P introduced to stop the sheet for positioningthe sheet to a fold position, and sheet detectors 16 and 17 detectingpassage of the sheet in the positions at a predetermined spacing fromthe stoppers 5 and 6 toward the inlets of the buckles 3 and 4.

The stoppers 5 and 6 are attached to belt driving mechanisms 7 and 8arranged along the first and second buckles 3 and 4. The position ofeach of the stoppers 5 and 6 is adjustable along a direction of thelength of the first and second buckles 3 and 4. The belt drivingmechanisms 7 and 8 comprise a pair of horizontal rollers 9 a, 9 b; 10 a,10 b are arranged at a spacing therebetween in a direction of the lengthof the buckles 3 and 4 and each extending in a direction of the width ofthe buckles, endless belts 12 and 13 extended through a pulley 11between the pair of rollers 9 a, 9 b; 10 a, 10 b, and motors 14 and 15driving one of the rollers 9 a; 10 a.

The stoppers 5 and 6 are attached to the endless belts 12 and 13. Withthe rotational motion of the endless belts 12 and 13 by driving of themotors 14 and 15, the stoppers 5 and 6 can be moved in the direction ofthe length of the buckles 3 and 4.

The sheet detectors 16 and 17 are connected to the associated stoppers 5and 6 through support members 18 and 19 and arranged ahead of thestoppers 5 and 6 in such a manner that the sheet detectors 16 and 17 canbe moved together with the associated stoppers 5 and 6. In this case,the sheet detectors 16 and 17 nay be arranged separately from thestoppers 5 and 6.

Five folding rollers 20 a to 20 e are arranged one above the other nearthe inlets of the first and second buckles 3 and 4 for rotation roundhorizontal axes extending in a direction of the width of the buckles 3and 4 in such a manner that the adjacent rollers are contacted with eachother. The folding rollers 20 a to 20 e have the same diameter. Amongthem, the three middle folding rollers 20 b, 20 c, and 20 d are formedas an idle roller. The uppermost folding roller 20 a and the lowermostfolding roller 20 e are formed as a driving roller.

A motor 23 is arranged for driving the uppermost folding roller 20 a andthe lowermost folding roller 20 e. A pulley 24 is fixed to the drivingshaft of the motor 23. Pulleys 21 a and 21 b are fixed to the rotationalaxes of the folding rollers 20 a and 20 e. An endless belt 22 isextended between the pulleys 21 a and 21 b and the pulley 24. The motor23 drives the folding rollers 20 a and 20 e, whereby the middle foldingrollers 20 b to 20 d are driven. In this embodiment, the folding rollers20 a to 20 e are driven by the single motor 23. The folding rollers 20 ato 20 e may be driven by plural motors, or, alternatively, the foldingrollers 20 a to 20 e may be driven by independent motors, respectively.

The folding rollers 20 a and 20 b function as a pair of rollers fornipping the sheet P so as to introduce it into the first buckle 3. Thefolding rollers 20 b and 20 c function as a pair of rollers for nippinga portion of the sheet P deflecting from the first buckle 3 so as tofold it. The folding rollers 20 c and 20 d function as a pair of rollersfor introducing the folded sheet P received from the folding rollers 20b and 20 c into the second buckle 4 with the folded portion in the lead.The folding rollers 20 d and 20 e function as a pair of rollers fornipping a portion of the sheet P deflecting from the second buckle 4 soas to it.

A feed roller 25 is arranged for rotation round a horizontal axis. Thefeed roller 25 is contacted with the uppermost folding roller 20 a so asto be rotated with the rotation of the folding roller 20 a.

The positions of the stoppers 5 and 6 are adjusted according to the foldposition of the sheet P. For instance, when the sheet P is folded intothree equal parts in its longitudinal direction, the stopper 5 isadjusted by actuating the belt driving mechanism 7 in such a manner thattwo-thirds of the length of the sheet P is introduced into the firstbuckle 3. In addition, the stopper 6 is adjusted by actuating the beltdriving mechanism 8 in such a manner that one-half of the length of thesheet P folded once by the first buckle 3 is introduced into the secondbuckle 4.

The uppermost sheet P of the sheet bundle placed on the sheet supplytable 1 is fed by the sheet feed roller 2 one by one, nipped between thefeed roller 25 and the folding roller 20 a and conveyed, and then nippedbetween the folding rollers 20 a and 20 b and introduced into the firstbuckle 3. The sheet P is stopped by the leading edge thereof coming intocollision with the stopper 5. The one-third length of the rear of thesleet P is still nipped between the folding rollers 20 a and 20 b so asto be conveyed to the first buckle 3, so that the sheet P is deflectedfrom the first buckle 3. The top of the deflected portion of the sheet Pis nipped between the folding rollers 20 b and 20 c and folded by them.

After the sheet P is folded once, the folded sheet P is discharged frombetween the folding rollers 20 b and 20 c. When the sheet P is foldedtwice, the sheet P folded by the folding rollers 20 b and 20 c isdelivered between the folding rollers 20 c and 20 d and introduced intothe second buckle 4 with the folded portion in the lead. The introducedsheet P is stopped by the leading edge thereof coming into collisionwith the stopper 6. The one-third length of the rear of the sheet P isstill nipped between the folding rollers 20 c and 20 d so as to beconveyed to the second buckle 4, so that the sheet P is deflected fromthe second buckle 4. The top of the deflected portion of the sheet P isnipped between the folding rollers 20 d and 20 e and folded by them. Thefolded sheet P is conveyed from the folding rollers 20 d and 20 ethrough a discharge belt 26 and a discharge roller 27 to a dischargetray 28.

According to the present invention, the sheet folding apparatus has acontrol section 29 outputting a signal for deceleration to the motor 23upon reception of a sheet detection signal from the sheet detectors 16and 17 and stopping output of the signal for deceleration after elapseof a predetermined time.

FIG. 3(A) is a timing diagram of control of the rotational speed of themotor by the control section, and FIG. 3(B) is a diagram illustratingsheet positions at points (i) and (ii) of the timing diagram of FIG.3(A). Referring to FIGS. 3(A) and 3(B), when the leading edge of thesheet P introduced into the first and second buckles 3 and 4 passesthrough the sheet detectors 16 and 17 (point (i)), the sheet detectionsignal is outputted from the sheet detectors 16 and 17 and received bythe control section 29. The control section 29 outputs the signal fordeceleration to the motor 23 upon reception of the sheet detectionsignal. The rotational speed of the folding rollers 20 a to 20 e isgradually reduced to decrease the conveying speed of the sheet P. Whenthe leading edge of the sheet P passes through the sheet detectors 16and 17 and the predetermined time elapses, the control section 29 stopsoutput of the signal for deceleration. In this embodiment, time from thestart to stop of output of the signal for deceleration is set in such amanner that the rotational speed of the folding rollers 20 a to 20 e isthe lowest when the leading edge of the sheet P collides with thestoppers 5 and 6 of the first and second buckles 3 and 4 (point (ii)),that is, that the speed of the motor 23 is the lowest immediately beforethe leading edge of the sheet P collides the stoppers 5 and 6.

When output of the signal for deceleration is stopped, the motor 23gradually increases the rotational speed. When the next sheet isintroduced into the first and second buckles 3 and 4, the rotationalspeed before being reduced is recovered. Along with it, the rotationalspeed of the rollers 20 a to 20 e is gradually increased. When the nextsheet is introduced into the buckles, the rotational speed before beingreduced is recovered.

The conveying speed of the sheet P introduced into the first and secondbuckles 3 and 4 is gradually reduced. When it is sufficiently reduced,the sheet P is stopped by the leading edge thereof coming into collisionwith the stoppers 5 and 6. It is possible to greatly reduce not only thenoise of collision of the sheet with the stopper but also the noise ofthe contact of the sheet with the inner wall surface of the buckle andthe noise of sheet nipping of the rollers. The noise level at operationof the sheet folding apparatus is considerably lowered. In addition, thefold position of the sheet is hardly fluctuated.

FIG. 4 is a side view illustrating the configuration of the sheetfolding apparatus according to another embodiment of the presentinvention and is similar to FIG. 1. The embodiment of FIG. 4 isdifferent from the embodiment of FIG. 1 in timing of rotational speedcontrol of the motor. The same constituent elements in FIG. 4 as thoseshown in FIG. 1 are indicated by similar numerals and the detaileddescription is omitted.

In this embodiment, as shown in FIG. 4, a sheet detector 30 is arrangedin the sheet conveying passage between the sheet feed roller 2 and thefeed roller 25. A rotary encoder 31 is mounted on the rotating shaft ofthe uppermost folding roller 20 a. In this case, the rotary encoder 31may be mounted on any one of the rotating shafts of the folding rollers20 b through 20 e, or, alternatively, the rotary encoder 31 may bemounted on the drive shaft of the motor 23 or the rotating shaft of thefeed roller 25. The control section 29 starts counting the number ofpulses outputted from the rotary encoder 31 upon reception of the sheetdetection signal from the sheet detector 30 to measure the conveyingdistance of the sheet P. The control section 29 outputs the signal fordeceleration to the motor 23 when the sheet P reaches a predeterminedposition, and stops output of the signal for deceleration when the sheetreaches the next predetermined position.

FIG. 5(A) is a timing diagram of control of the rotational speed of themotor by the control section 29, and FIG. 5(B) is a diagram illustratingsheet positions at points (i) and (ii) of the timing diagram of FIG.5(A). Referring to FIGS. 5(A) and 5(B), when the leading edge of thesheet P fed from the sheet feed roller 2 passes through the sheetdetector 30, the sheet detection signal is outputted from the sheetdetector 30 and received by the control section 29. The control section29 starts counting the number of pulses outputted from the rotaryencoder 31 upon reception of the sheet detection signal to measure theconveying distance of the sheet. The control section 29 outputs thesignal for deceleration to the motor 23 when the leading edge of thesheet P reaches a predetermined position (point (i)) ahead of thestoppers 5 and 6 of the buckles 3 and 4. Thereafter, the control section29 stops output of the signal for deceleration when the sheet P reachesthe next predetermined position (point (ii)), in this embodiment, theposition in which the leading edge of the sheet P collides with thestoppers 5 and 6. After the sheet P is introduced into the buckles 3 and4 to pass through the predetermined position, the rotational speed ofthe rollers 20 a to 20 e is gradually reduced to decrease the conveyingspeed of the sheet P. The leading edge of the sheet P collides with thestoppers 5 and 6 at a sufficiently reduced speed and the sheet P isstopped. Thereafter the rotational speed of the rollers 20 a to 20 e isgradually increased. The rotational speed before being reduced isrecovered when the next sheet P is introduced into the buckles 3 and 4.This embodiment can bring about the same effect as that of theembodiment of FIG. 1.

1. A sheet folding apparatus having: at least one buckle (3, 4) in whicha sheet (P) to be folded is introduced to a length corresponding to apredetermined fold position, said at least one buckle (3, 4) beingprovided with a position adjustable stopper (5, 6) for stopping theintroduced sheet (P) by coming into collision with the leading edge ofthe sheet (P) so as to position the sheet (P) in said fold position; apair of rotating rollers (20 a, 20 b; 20 c, 20 d) arranged near theinlet of said buckle (3, 4) and oppositely to each other for taking thesheet (P) in said buckle (3, 4); and a pair of rotating rollers (20 b,20 c; 20 d, 20 e) arranged near the inlet of said buckle (3, 4) andoppositely to each other for folding a portion of the sheet (P)deflecting from said buckle (3, 4), the sheet folding apparatuscharacterized by a sheet detector (16, 17) arranged at a predeterminedspacing from said stopper (5, 6) of said buckle (3, 4) toward the inletof said buckle (3, 4) and detecting passage of the sheet (P); and acontrol section (29) outputting a signal for deceleration to a drivingsource (23) of said roller (20 a to 20 e) upon reception of a sheetdetection signal from said sheet detector (16, 17) and stopping outputof said signal for deceleration after elapse of a predetermined time,whereby, after the leading edge of the sheet (P) introduced into saidbuckle (3, 4) passes through said sheet detector (16, 17), therotational speed of said rollers (20 a to 20 e) is reduced to decreasethe conveying speed of the sheet (P), the leading edge of the sheet (P)comes into collision with said stopper (5, 6) at a sufficiently reducedspeed, and thereafter the rotational speed of said roller (20 a to 20 e)is gradually increased so that the rotational speed before being reducedis recovered when the next sheet (P) is introduced into said buckle (3,4).
 2. A sheet folding apparatus having: at least one buckle (3, 4) inwhich a sheet (P) to be folded is introduced to a length correspondingto a predetermined fold position, said at least one buckle (3, 4) beingprovided with a position adjustable stopper (5, 6) for stopping theintroduced sheet (P) by coming into collision with the leading edge ofthe sheet (P) so as to position the sheet (P) in said fold position; apair of rotating rollers (20 a, 20 b; 20 c, 20 d) arranged near theinlet of said buckle (3, 4) and oppositely each other for taking thesheet (P) in said buckle (3, 4); and a pair of rotary drive rollers (20b, 20 c; 20 d, 20 e) arranged near the inlet of said buckle (3, 4) andoppositely to each other for folding a portion of the sheet (P)deflecting from said buckle (3, 4), the sheet folding apparatuscharacterized by a sheet detector (30) arranged upstream of the pair ofrollers (20 a, 20 b) for taking the sheet (P) in the uppermost streambuckle (3) for detecting passage of the sheet (P); a rotary encoder (31)mounted on at least one rotating shaft of said rollers (20 a to 20 e)arranged near the inlet of said buckle (3, 4) or at least one anotherrotating shaft rotatable in conjunction with said rotating shaft of saidrollers (20 a to 20 e); and a control section (29) starting counting thenumber of pulses outputted from said rotary encoder (31) upon receptionof a sheet detection signal from said sheet detector (30) to measure theconveying distance of the sheet (P), outputting a signal fordeceleration to a driving source (23) of said roller (20 a to 20 e) whenthe sheet (P) reaches a predetermined position, and stopping output ofsaid signal for deceleration when the sheet (P) reaches the nextpredetermined position, whereby, after the leading edge of the sheet (P)passes through said sheet detector (30), the rotational speed of saidroller (20 a to 20 e) is reduced to decrease the conveying speed of thesheet (P), the leading edge of the sheet (P) comes into collision withsaid stopper (5, 6) at a sufficiently reduced speed, and, thereafter,the rotational speed of said roller (20 a to 20 e) is graduallyincreased so that the rotational speed before being reduced is recoveredwhen the next sheet (P) is introduced into said buckle (3, 4).